Magnetic Properties of Ferrites: Ferrimagnetism and Antiferromagnetism.) Ann

Magnetic properties of ferrites : ferrimagnetism and antiferromagnetism Louis Néel

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Louis Néel. Magnetic properties of ferrites : ferrimagnetism and antiferromagnetism. Physical Chem- ical & Earth Sciences, 1984, pp.18. hal-03070529

HAL Id: hal-03070529 https://hal.archives-ouvertes.fr/hal-03070529 Submitted on 15 Dec 2020

HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. CC/NUMBER 31 _Tfifs week's citation Classic: JULY 30, 1984 Néel L. Propriétés magnétiques des ferrites: ferrimagnétisme et antiferromagnétisme. (Magnetic properties of ferrites: ferrimagnetism and antiferromagnetism.) Ann. Phys. Paris 3:137-98, 1948. [Faculté des Sciences, Üniv. Grenoble, France]

This report introduced and studied a new category in 19383 of bodies possessing such properties, is a of magnetic substances, ferrimagnets, which are particular case of ferrimagnetism where the two added to those already known: the diamagnets, sub-lattices are identical, with equal spontaneous paramagnets, and ferromagnets. Ferrimagnetism magnetizations, and opposed to all temperatures. plays an important part in industrial applications. "My work of 1948 predicted the existence of [The SC7® indicates that this paper has been cited substances of which the spontaneous attraction in over 595 publications since 1955, making it the presents very unusual abnormal thermal varia- most-cited paper ever published in this journal ] tions. All these anomalies were ultimately re- trieved experimentally, as, for example, those where the spontaneous magnetization counter- balance, in a sense, is at a certain compensation Louis Néel temperature. At this temperature, the spontaneous 15, rue Marcel-Allégot A magnetizations and B magnetizations are equal 92190 Meudon and opposed to each other. Lithium-chrome fer- France rite4-6 as well as some garnets7 are examples of this. 8 9 February 24, 1984 "In 1954, ' the theory of ferrimagnetism con- tributed a great deal to the discovery of a new and "Since 1947, the magnetic properties of spinel very rich family of ferrimagnetic substances: the 7 ferrites (the general formula Fe203M0, where M is rare earth garnet ferrites of the form Fe5T3012, a bivalent metal) have remained completely unex- where T is a rare earth and where a trivalent ele- plained. The article in question, which was accept- ment can be substituted for Fe. Many samples ed with only a bit of reticence by the editorial from this family have found interesting applica- committee of the Annales de Physique, gives a tions, such as yttrium garnets. complete and quantitative interpretation of these "Since 1948, thousands of publications have properties, based on a large number of outside ex- been written on the subject of ferrimagnetism and perimental results. It shows that there exists a new one can also say that their magnetic properties are category of magnetism: ferrimagnetism. In classi- better understood than those of metallic ferromag- cal ferromagnets, tike iron or nickel, the interac- nets. Considering the great interest in ferrimagne- tions between atomic magnetic moments tend to tism for basic physics and the knowledge of the align themselves parallel to each other in the same different types of magnetic interactions, the im- sense; that is, at low temperature all these portance and the variety of applications are con- moments become parallel. On the contrary, in fer- siderable. Many of these bodies are insulators, and rimagnets, the magnetic atoms are shared between even excellent electrical insulators, such as gar- two distinct A crystalline and B crystalline sub- nets. They can thus be used in very high frequency lattices. At low temperature, the macroscopic methods, such as in radar. These applications are spontaneous attraction is equal to the difference facilitated by the possibility of preparing them in of spontaneous attraction of the two sub-lattices. large monocrystals. "Antiferromagnetism, of which I predicted the "For this discovery, I won the Nobel prize in existence as early as 1932,3,2 before the discovery 1970, as well as other distinctions."

1. Néel L. Influence des fluctuations du champ moléculaire sur les propriétés magnétiques des corps. Ann. Phys. Pans 18:5-105, 1932. 2. Nfel L. Theory of constant paramagnetism. Application to manganese. CR Acad. Sci. Paris 203:304-6, 1936. 3. Blzene H, Squire CFA TsaTB. Transition point of magnetic susceptibility of MnO. CR Acad. Sci. Paris 207:449-50. 1938. 4. Gorter E W. Saturation magnetization and crystal chemistry of ferrimagnetic oxides. Philips Res. Rep. 9:295-320, 1954. (Cited 250 times since 1955.) 5...... Saturation magnetization and crystal chemistry of ferrimagnetic oxides. 2. Theory of ferrimagnetism. Philips Res. Rep. 9:321-65, 1954. (Cited 100 times since 1955.) 6...... Saturation magnetization and crystal chemistry of ferrimagnetic oxides. 3. Saturation moment and physical chemistry of ferrimagnetic spinels containing titanium. Philips Res. Rep. 9:403-43, 1954. (Cited 135 times since 1955.) 7. Néel L, Pautbenct R A Dreyfus B. The rare earth garnets. Prog. Low Temp. Phys. 4:344-83, 1964. 8. Pautbenet R A Blum P. Thcnnomagnetic study of gadolinium ferrite. CR Acad. Sci. Paris 239:33-5, 1954. 9. Néel L. The interpretation of the magnetic properties of the rare earth ferrites. CR Acad. Sci. Paris 239:8-11, 1954.